Unit 1: CHEMICAL CHANGES AND STRUCTURE Flashcards
1
Q
What is the difference between a chemical and physical change?
A
A chemical change results in the formation of new substances, while a physical change does not.
2
Q
What does the term endothermic refer to?
A
Endothermic describes a reaction that absorbs energy, usually in the form of heat.
3
Q
What does the term exothermic refer to?
A
Exothermic describes a reaction that releases energy, usually in the form of heat.
4
Q
How can the progress of chemical reactions be followed?
A
By measuring changes in mass, volume, and other quantities.
5
Q
List the ways to increase the rate of reaction.
A
- Increasing temperature
- Increasing concentration of a reactant
- Increasing surface area/decreasing particle size
- Adding a catalyst
6
Q
What are catalysts?
A
Substances that speed up chemical reactions but can be recovered chemically unchanged at the end of the reaction.
7
Q
How is the average rate of a chemical reaction calculated?
A
Average rate = change in quantity / time taken.
8
Q
True or False: The rate of a reaction always increases over time.
A
False.
9
Q
What is the definition of an element?
A
A substance that contains only one kind of atom.
10
Q
What is a compound?
A
A substance formed when atoms of two or more different elements are chemically joined.
11
Q
What is a mixture?
A
A combination of two or more substances that are not chemically joined.
12
Q
Define solubility.
A
The ability of a substance to dissolve in a liquid.
13
Q
What is a saturated solution?
A
A solution in which no more solute can dissolve.
14
Q
List the three states of matter.
A
- Solid
- Liquid
- Gas
15
Q
What is the melting point?
A
The temperature at which a solid becomes a liquid.
16
Q
What is the boiling point?
A
The temperature at which a liquid becomes a gas.
17
Q
How are elements arranged in the Periodic Table?
A
In order of increasing atomic number.
18
Q
What defines the elements in a group of the Periodic Table?
A
They have the same number of outer electrons.
19
Q
What is the charge of protons and electrons?
A
- Protons: one-positive
- Electrons: one-negative
20
Q
What is the approximate mass of protons and neutrons?
A
Both have a mass of approximately one atomic mass unit.
21
Q
What is the mass number of an atom?
A
The sum of the number of protons and neutrons.
22
Q
Define isotopes.
A
Atoms with the same atomic number but different mass numbers.
23
Q
What does nuclide notation show?
A
The atomic number, mass number, and charge of atoms or ions.
24
Q
What are covalent bonds?
A
Bonds formed between non-metal atoms through shared pairs of electrons.
25
List the seven diatomic molecules.
* H2
* N2
* O2
* F2
* Cl2
* Br2
* I2
26
What is the characteristic of covalent molecular substances?
They have low melting and boiling points due to weak intermolecular forces.
27
What is the structure of ionic compounds?
Lattice structures of oppositely charged ions.
28
Why do ionic compounds have high melting and boiling points?
Strong ionic bonds must be broken to disrupt the lattice structure.
29
Under what conditions do ionic compounds conduct electricity?
When molten or in solution.
30
What is the general charge of metal ions?
They typically lose electrons and form positive ions.
31
What is the general charge of non-metal ions?
They typically gain electrons and form negative ions.
32
What is an ion-electron equation?
An equation that shows the formation of ions through the loss or gain of electrons.
33
What is the significance of the relative atomic mass?
It is the average mass of the isotopes of an element, weighted by their relative abundance.
34
Fill in the blank: A substance that can conduct electricity must contain _______.
charged particles that are free to move.
35
What is the electron arrangement of a sodium ion, Na+?
2,8.
36
What are the properties of covalent network structures?
* Very high melting and boiling points
* Do not dissolve
* Do not conduct electricity
37
What does it mean for a substance to be soluble in water?
It can dissolve in water.
38
True or False: All ionic compounds are soluble in water.
False.
39
Why do ionic compounds not conduct electricity when solid?
The ions are held in a lattice and are not free to move.
40
What does the ending '-ide' in a compound name indicate?
It indicates that the compound contains two elements.
41
What do the endings '-ite' or '-ate' in a compound name signify?
They indicate that oxygen is also present in the compound.
42
How can chemical formulae be written for two element compounds?
Using valency rules and a Periodic Table.
43
What is the purpose of Roman numerals in compound names?
To indicate the valency of an element.
44
What does the chemical formula of a covalent molecular substance represent?
The number of each type of atom present in a molecule.
45
What does the formula of a covalent network give?
The simplest ratio of each type of atom in the substance.
46
What are ions containing more than one type of atom called?
Group ions.
47
What do ionic formulae represent?
The simplest ratio of each type of ion in the substance, including charges.
48
How should charges and numbers of atoms/ions be formatted in formulae?
Charges must be superscript and numbers of atoms/ions must be subscript.
49
What is the definition of a mole?
A mole is the amount of substance that contains as many entities as there are atoms in 12 grams of carbon-12.
50
What is the gram formula mass (GFM) of a substance?
The mass of one mole of a substance in grams.
51
What is the relationship between the mass and number of moles of a substance?
Mass (g) = Number of moles x Gram formula mass (g).
52
What is produced when a solute is dissolved in a solvent?
A solution.
53
What can be calculated from the mass of solute, number of moles, volume, or concentration of a solution?
The mass of solute, number of moles, volume of solution, or concentration of the solution.
54
What does a balanced chemical equation show?
The same number and type of atoms on each side of the equation.
55
What is the formula for calculating percentage composition of an element in a compound?
% mass of element = (mass of element in compound / gram formula mass) x 100%
56
What is the pH scale an indication of?
The hydrogen ion concentration.
57
What is a neutral solution characterized by?
Equal concentrations of H+(aq) and OHˉ(aq) ions.
58
What does the symbol in a reversible reaction indicate?
That the reaction occurs in both directions.
59
What environmental problems are linked to increased production of carbon dioxide, sulphur dioxide, and oxides of nitrogen?
Acid rain, global warming, and ocean acidification.
60
When using prefixes in compound names, what does 'di' indicate?
That there are two atoms or ions of a particular type.
61
What is the formula for silicon hydride?
SiH4.
62
What is the formula for calcium sulfide?
CaS.
63
What is the formula for aluminium oxide?
Al2O3.
64
What does the cross-valency method help to determine?
The formulae for substances containing two elements.
65
What is the gram formula mass of water (H2O)?
18g.
66
How many moles are in 69 g of potassium carbonate (K2CO3)?
0.5 moles.
67
What is the concentration of a 500 cm3 solution of 5.85 g of NaCl?
0.2 mol/l.
68
What mass of calcium hydroxide is needed to produce 500 cm3 of a 0.1 mol/l solution?
3.7 g.
69
What is the formula for sodium carbonate?
(Na+)2CO32-.
70
What is the formula for the reaction between magnesium and dilute sulphuric acid?
Mg + H2SO4 → MgSO4 + H2.
71
What is the molar ratio in a balanced equation?
It shows the relative amounts of reactants and products.
72
What is the effect of rust remover on iron(III) oxide?
It converts iron(III) oxide into iron(III) phosphate.
73
What is the formula for calculating the number of moles in a solution?
n = v x c.
74
What is the GFM of sodium chloride (NaCl)?
58.5 g.
75
What is the GFM of potassium carbonate (K2CO3)?
138 g.
76
What is the significance of calculating the percentage of an element in a compound?
It helps in the production of fertilizers and in metal chemistry.
77
What does a concentrated solution contain?
A high proportion of solute to solvent.
78
What happens when a concentrated solution is diluted?
More solvent is added to reduce the concentration.
79
What indicates a reversible reaction?
The ⇌ symbol
## Footnote
It shows that the reaction can proceed in both forward and reverse directions.
80
What is the pH of a neutral solution?
pH = 7
## Footnote
In a neutral solution, the concentration of H+ ions equals the concentration of OH- ions.
81
What happens to the pH of an acidic solution when it is diluted with water?
The pH will increase towards 7
## Footnote
This occurs as the concentration of H+ ions decreases.
82
What is the relationship between hydrogen and hydroxide ions in an acidic solution?
H+ concentration > OH- concentration
## Footnote
Acidic solutions have a pH below 7.
83
What is the relationship between hydrogen and hydroxide ions in an alkaline solution?
H+ concentration < OH- concentration
## Footnote
Alkaline solutions have a pH above 7.
84
What do soluble non-metal oxides form when dissolved in water?
Acidic solutions
## Footnote
They increase the concentration of H+ ions.
85
What do soluble metal oxides form when dissolved in water?
Alkaline solutions
## Footnote
They increase the concentration of OH- ions.
86
What is a neutralisation reaction?
A reaction between a base and an acid producing water and a salt
## Footnote
The general equation is: acid + base → salt + water.
87
What types of substances can neutralise acids?
Metal oxides, metal hydroxides, metal carbonates, and ammonia
## Footnote
These substances are classified as bases.
88
What is the formula for the dissociation of water?
H2O(l) ⇌ H+(aq) + OH-(aq)
## Footnote
This equation represents the equilibrium between water molecules and ions.
89
What is the purpose of an indicator in a titration?
To show the end-point of the reaction
## Footnote
It helps determine when the neutralisation is complete.
90
What is the effect of dilution on the pH of an alkaline solution?
The pH will decrease towards 7
## Footnote
This occurs as the concentration of OH- ions decreases.
91
What do spectator ions do in a reaction?
They remain unchanged
## Footnote
Spectator ions are present in the reaction but do not participate in the actual reaction.
92
What is the balanced ionic equation for the reaction of H+ and OH-?
H+(aq) + OH-(aq) → H2O(ℓ)
## Footnote
This equation represents the neutralisation of an acid and a base.
93
What is the first part of the name of a salt derived from?
The positive ion within the base
## Footnote
The second part comes from the acid used.
94
What is the pH range of acidic solutions?
pH < 7
## Footnote
These solutions have a higher concentration of H+ ions than OH- ions.
95
What is the pH range of alkaline solutions?
pH > 7
## Footnote
These solutions have a higher concentration of OH- ions than H+ ions.
96
What is the general reaction for a metal carbonate and an acid?
Metal carbonate + acid → salt + water + carbon dioxide
## Footnote
This is a specific type of neutralisation reaction.
97
How can soluble salts be prepared using neutralisation reactions?
By reacting an acid with a base and evaporating the solution
## Footnote
The process can involve titration to determine accurate volumes.
98
What is the formula for the reaction of sulfuric acid with calcium carbonate?
H2SO4(aq) + CaCO3(s) → CaSO4(aq) + H2O(l) + CO2(g)
## Footnote
This illustrates a neutralisation reaction producing a gas.
99
What is an alkali?
A base that is soluble in water
## Footnote
It neutralises acids and increases the concentration of OH- ions.
100
What type of acid is produced from sulfur dioxide dissolving in water?
Sulfuric acid
## Footnote
The reaction is SO2(g) + H2O(l) → 2H+(aq) + SO42-(aq).
101
What is the pH of a solution with equal concentrations of H+ and OH- ions?
pH = 7
## Footnote
This indicates a neutral solution.
102
What happens to the concentration of H+ ions in a solution when it becomes more acidic?
The concentration of H+ increases
## Footnote
This results in a pH decrease.
103
What is the term for the concentration of H+ ions in a solution?
Hydrogen ion concentration
## Footnote
It is measured on the pH scale.
104
What is the general equation for a neutralisation reaction involving a base?
Base + acid → salt + water
## Footnote
This represents the basic concept of neutralisation.
